Postnatal changes in blood spot 17-hydroxyprogesterone level in healthy preterm and full-term neonates

Blood spot 17OH-P concentrations were determined in 14 healthy premature (mean birthweight 1439 g, mean gestational age 30 weeks) and full-term newborn infants (mean birthweight 3532 g, mean gestational age 39.2 weeks) during the first five weeks of life to provide reference data for infants with various gestational and postnatal ages. It was demonstrated that with advancing age there was an abrupt fall in 17OH-P from 296.2 +/- 84.1 nmol/l on the first day to 101.2 +/- 19.5 nmol/l on the 7th day (p less than 0.001) and 75.7 +/- 8.7 nmol/l (p less than 0.05) on the 14th day in premature infants. In full-term neonates its initial value is much lower (90.1 +/- 12.5 nmol/l) and its fall during the first week is much less pronounced (51.5 +/- 6.5 nmol/l, p less than 0.01). Comparing the postnatal changes in 17OH-P in the two groups it proved to be significantly higher in premature than in full-term infants at all ages except for the 4th week. When blood spot 17OH-P values were studied as a function of gestational age at the age of 5 days a significant inverse relationship was found between the two parameters. It is assumed that in addition to placental 17OH-P production and perinatal stress, renal salt wasting may also account for the long lasting elevation of 17OH-P plasma level seen in premature infants.